Apparatus for filling a sample volume defining device

ABSTRACT

An apparatus for filling a sample volume defining device for separating at least one small defined volume of a liquid sample from a relatively larger undefined volume of said sample, said device including a first body and a second body movable relative to each other, whereby said first body has at least one cavity in a surface thereof, said at least one cavity having said defined volume. One of said first or said second body has at least one inlet opening adapted to be placed in a drop of the liquid sample. A defined channel is provided between said first and second body, which channel has fluid connection with said at least one opening and at least beyond said at least one cavity whereby the dimensions of said channel being such that said channel and said at least one cavity is filled with said liquid sample.

FIELD OF THE INVENTION

The present invention relates an apparatus for filling a sample volumedefining device, particularly a disposable sample volume definingdevice, for separating at least one small defined volume of a liquidsample from a relatively larger undefined volume of said sample, saiddevice including a first body and a second body movable relative to eachother, whereby said first body has at least one cavity in a surfacethereof, said at least one cavity having said defined volume, and saidsecond body includes a means slidable along said surface and over saidat least one cavity upon relative movement of said bodies, whereby saiddefined volume is achieved in said at least one cavity. The liquidsample is a blood sample, for instance.

BACKGROUND OF THE INVENTION

In blood testing, it is of crucial importance to define an accuratevolume of a blood sample, since such accurately defined volume is lateron used for certain tests. The accurately defined volume of blood sampleis normally diluted by an accurately defined volume of a diluent or alysing agent, in order to obtain a dilution of typically 1:100 to1:80000. When counting white blood cells is concerned the dilution istypically 1:400 and when counting red blood cells (RBC) is concerned thedilution is typically 1:40000, in the latter case the dilution normallytaking place in two steps. It is obvious, that measurement of samplevolumes and dilution liquid volumes must be performed in an accurate andrepeatable way such that a correct degree of dilution can always beguaranteed. Apparently, accurate measurement of sample volumes is acritical step in the dilution procedure, since the volumes concerned areextremely small compared to the corresponding diluent volumes.

To be able to obtain an accurate volume of a blood sample it is ofcrucial importance that the means in which the blood sample is containedis filled in a very precise and accurate and repeatable way.

A sample volume defining device of the above-identified type is knownfrom the co-pending Swedish Patent Application No. 0303157-2. It hasusually the form of a disposable cassette.

One problem when filling small cavities or voids or the like forobtaining the accurate and repeatable volume of a liquid sample,preferably a blood sample, is that the cavities are not filled in aproper way due to the formation of air bubbles in the cavities designedfor the blood sample. Thus, there will be a difference in the volumebetween different blood samples and this will have a large significancewhen later counting the blood cells.

Another problem with known apparatus for testing of small volumes of aliquid sample/blood sample is to see when the apparatus is correctlyfilled.

Another problem is that the filling of known apparatus for testing ofsmall volumes of a liquid sample/blood is dependent upon the directionof the apparatus when it is filled.

SUMMARY OF THE INVENTION

The object of present invention is to providing an apparatus for fillinga sample volume defining device comprising at least two relativelymovable bodies, one of which is provided with at least one cavity to befilled with liquid sample, for separating at least one accuratelydefined volume of a liquid sample from a relatively larger undefinedvolume of said sample.

A further object is to provide an apparatus of the above type in whichit is easy to see when the cavity is filled with the liquid sample in anaccurate and repeatable way.

A further object is to achieve an apparatus of the above type which isnot dependent upon the filling direction.

Said object is achieved according to the present invention by anapparatus which is characterized in that that one of said first or saidsecond body has at least inlet opening adapted to be connected with adrop of the liquid sample, that a defined channel is provided betweensaid first and second body, which channel has fluid connection with saidat least one inlet opening and at least beyond said at least one cavity,and that the dimensions of said channel being such that said channel andthereby said at least one cavity is filled with said liquid by capillaryforce.

As indicated a sample volume defining device is known from theco-pending application SE 0303157-2, incorporated by reference herein.Basically the volume defining process incorporates a) application of arelatively larger, often undefined, volume of the sample onto a surfaceand into a cavity formed in the surface and b) moving a scraping edgeover the surface to leave a smaller defined volume of the sample in, thecavity. Further processing steps may follow, such as c) flushing thecavity with a liquid, such as a solution or reagent, to obtain a dilutedsample, d) mixing the sample and diluent to obtain a homogenous dilutedsample and e) performing measurements on the diluted and mixed sample.

For purposes of discussion the surface can be regarded as a referencesurface, comprising the physical surface as well as an imaginarysurface, flush and continuous with the physical surface, or defined inmechanical terms by movement of a thought entirely rigid scraper meansin contact with the surface, across the cavity so as to define a targetvolume of the cavity limited by the imaginary surface. The referencesurface shall at least surround the cavity to such an extent as to allowthe scraping action and preferably the reference surface encircles thecavity on all sides.

The reference surface may have different shapes as long as it meets thecontinuity requirement, consistent with the scraping purpose. Forexample, the reference surface with its cavity may be double-curved,meaning that it cannot be formed by bending a flat surface, asexemplified with a cavity in a ball valve, or the reference surface maypreferably be single-curved, meaning that it can be formed from a flatsurface, as exemplified by a cavity in a cylinder valve, or mostpreferably it is substantially flat, as exemplified by a cavity in aslide valve.

The cavity size, i.e. the target volume under the imaginary surface, orrather the practical surface to be further discussed below, depends onseveral factors. Some of these factors are application dependent, suchas sample nature and necessary volumes for planned dilution degrees orrequirements for intended measurement. In disposable devices, foreconomical, reasons it is generally desirable to minimize the volumes inorder also to minimize other features such as diluent volumes, mixingarrangements etc. However, manual manipulation and manufacturingconstraints, e.g. molding of plastics, may place a lower limit topractical or possible cavity sizes. In case of several cavities, e.g.for different dilution degrees, the restrictions typically are set bythe smallest cavity. General values are difficult to give but experiencehas indicated that the cavity volume should preferably be larger than0.01 μl, preferably larger than 0.05 and most preferable larger than 0.1μl. The maximum cavity volume can be kept below 50 μl, preferably below25 μl and most preferably below 15 μl.

Similarly cavity shape may be determined by several factors. Besidesmanufacturing constraints that may put limits to advanced features ofsmall cavities, desirable shape is mainly dictated by efficient fillingand foreseeable, also expressed herein as reproducible, scrapingresults, of particular importance between different disposable devices.

Cavity filling may take place in various ways. As indicated, if a samplesurplus is simply placed on the cavity there is a risk for gas inclusionand unfilled voids in the cavity. To avoid this the sample may be forcedinto the cavity, e.g. by a sample stream positively pumped by forcedflow past the cavity, which, however, does not entirely secures flowthrough the cavity. Preferably then forced filling is made by insertionof a probe straight above or into the cavity, preferably with care takenagainst probe outlet contact and blocking, which cannot easily becompensated by increased injection pressure due to the hydraulic arearelationship, and with necessary precision care needed for smallcavities.

A preferred filling method is use of capillary forces for filling. It isbelieved that such filling takes place by wetting of liquid attractionsurfaces highly independent of other forces applied to the liquidsample. Hence the criteria for capillary filling shall be regardedsatisfied, and accordingly testable, if filling takes place, or can takeplace, without other forces applied. The criteria for filling withoutother forces applied is testable also in devices designed forapplication with other forces, e.g. syringe or gravity filling of sampleinto a channel designed for capillary filling. The non-presence ofadditional forces shall exclude forces needed to initiate capillaryfilling, which may require forced introduction of the liquid into achannel designed for capillary filling, e.g. forced wetting of a certainpart of channel circumference for the capillary filling to continueautonomously. Capillary filling requires a certain surface to volumeratio to proceed, which ratio depends mainly on dimensions but also onamong others on liquid to surface wetting attraction, the surfacepossibly being material selected or modified by plasma treatment,chemical modification, surface treatment etc., normally requiring acertain circumference length in relation to cross-section, whichcircumference need not be continuous but preferably forms asubstantially closed channel. Capillary filling requirements are givenby example herein, which requirements, however, should be determined forthe actual materials and liquids involved.

Initiation of filling can be made in different ways. The supply can bemade substantially along the reference surface, giving advantages incapillary wetting proceeding in the same direction as feeding. Thesupply can preferably be made from below, i.e. through the samestructure that carries the cavity or cavities and with a flowsubstantially opposite to that needed for filling the cavity, e.g. forthe purpose of avoiding interference with the structures introduced tostop capillary filling spreading laterally in the channel. The supplycan most preferably be made from above the reference surface, e.g. forthe purpose of the above proposes, for gravity assistance, forsimplicity in the design and for the possibility of closing the feedingopening during the scraping arrangement movement.

The sample introduction site is preferably designed to assist in theabove objects. Preferably the site is designed for compatibility withboth direct sample introduction, e.g. a blood drop applied to the site,or device introduction for example by means of a syringe, a probe etc. Apreferred design is a funnel ending in the capillary channel, preferablyarranged for stopping devices against too deep penetration for reasonsgiven, and most preferably having a narrowest flow area preferably beinglarger than that required for capillary feeding, thereby assisting ingravity filling, preferably, however, being noncircular, preferablyslit-formed, for proper transition between non-capillary and capillaryflow. For similar reasons the funnel preferably has a diverging portionafter its narrowest part, giving an overall shape of an hour-glass, witha diverging outlet angle adapted for capillary flow for proceeding.

Common in the art are capillary tubes for aspiration of samples. Thecurrent cavities differs from such tubes in that the cavities extendfrom a reference surface, which reference surface in itself forms partof a sample filling channel in general, but preferably a filling channeldesigned for capillary filling, preferably lateral to cavity fillingflow direction. The volume and shape of the filling channel areirrelevant as long as the cavity volume is well defined. The fillingchannel may comprise several cavities without major modifications of thereference surface carrying device. Filling of cavities arranged remotefrom, or at least not directly under, channel feeding structures avoidsinterference with any possible channel feeding device or probe as wellas possible later flushing. Simplicity adds advantages over known valvetype arrangements.

Without being bound by theory it is believed that capillary filling isdriven by liquid affinity to surface and accordingly filling by thismechanism should be facilitated in general terms by a large surface tovolume ratio. For a suitable capillary filling design, cavity size andshape come into play. Spherical shapes have the least surface to volumeratio. On the other hand small cavities generally have a larger surfaceto volume ratio than larger cavities, representing a further argumentfor minimization, a further merit of the present invention to haverealized. Accordingly shape is less important for small cavities whereeven forms close to spherical or partially spherical can be accepted,whereas larger cavities with preference are given a shape with higherthan, partial or full, spherical surface to volume ratio, e.g. tube orchannel forms. The distinction between “smaller” and “larger”respectively can herein roughly be understood as cavities having depths“shallower” and “deeper” respectively than double the minimum requiredfor capillary flow to proceed in a continuous channel of that dimension.The reason the cavities can be deeper than the capillary minimum isbelieved to be that the channel, of capillary dimensions, provides ariver of liquid drag that locally, i.e. at the cavities, can overwhelmlarger dimensions locally.

Due to the surface wetting theory, it is further believed that sharpedges are easily traversed by a capillary driven liquid front if theedge is concave, i.e. a surface angle in the intersection of less than180°, as seen from the wet side, whereas convex edges, i.e. a surfaceangle in the intersection of more than 180°, are less easily traversed.Accordingly it is preferred that that at least the convex edges aresmoothed out to facilitate capillary flow transfer by reducing theangle. This preferably applies to the arrival direction of the capillaryflow front, i.e. the up-flow end, whereas the other end, i.e. down-flowend, is regarded less critical.

In summary, at least larger cavities should be designed for facilitatedcapillary filling. Smaller cavities are less critical and, furthermore,common manufacturing methods such as plastic moulding normally result insmoothed out transition surfaces, beneficial for capillary filling. Atleast the larger cavities are preferably shaped elongated, i.e. havingan imaginary surface with a longer axis and a shorter axis perpendicularthereto, which gives an increased circumference to area ratio inrelation to a circle, which elongated shape can take a variety of formssuch as elliptical, rectangular etc. In case of more complicated formsthese can be compared with elliptical shape of the same area fordetermination of the longer and shorter axes. Preferably such a cavityis located with at least a vector component and preferably its full longaxis parallel with the capillary filling flow direction, i.e. withrespect to the arriving capillary liquid front, herein referred to asthe up-flow direction. The elongated form secures that the cavity has anincrease surface to volume ratio in relation to the minimal possible. Itis further preferred that the cavity up-flow end has a slow descendingslope down into the cavity, as seen in the liquid flow direction, andfurthermore that the cavity sides substantially parallel to the flowdirection are steep with respect to the reference surface.

The cavity may have several openings, or entrances, e.g. the cavity mayform a tube extending between two openings as in known capillary tubesalthough here also connecting to a capillary driven filling channel. Itis preferred, however, that to the extent the channel has more than oneopening these opens into one and the same reference surface. Mostpreferably the cavity has only one opening for best filling and scrapingproperties.

A sloping arrangement is consistent with a cavity design narrowing awayfrom the reference surface and, in case of cavities with only oneopening, towards its bottom or, differently expressed, thatcross-sections taken parallel with the reference surface have decreasingcavity areas when moving away from the reference surface, at least overa part of the cavity depth and preferably over substantially the cavityfull depth. It is further preferred that the cavity walls are at leastsubstantially perpendicular but preferably converging towards the cavitybottom, the bottom being the end farthest away form the referencesurface. Most preferably small or no undercut parts are present in thecavity.

Filling of the cavity or cavities is facilitated if the cavity isdesigned assist in capillary filling, meaning that cavity surface tovolume ratio, at least in the sample flow direction, meets the capillaryfilling requirement. If the channel has sufficiently strong surfaceaffinity the cavity surfaces may exceed the surface to volumerelationship for capillary filling but preferably the cavity dimensionslies within that of the capillary filling requirements, disregardinghere the additional dimensions provided by the channel.

Discussing next the scraping, the imaginary surface has been describedabove as an idealized surface entirely continuous with the referencesurface. However, in practice any scraping device able to be kept ingood contact with the reference surface must have a certain resilience,preferably the minimum resilience necessary for dynamic adaptation tothe reference surface, which is preferably made of a harder material,without undue further deformation. Certainly the material in thescraping device should not be soft, in the sense that it easily deformspermanently. Suitable materials may include thermoplastics andpreferably eleastomerics. The scraper resilience means that it willexpand by deflection to a certain extent into the cavity volume, therebycreating an actual, or practical, opening surface for the cavity,generally so as to reduce the cavity volume somewhat. This may not be aproblem as long as the reduction is predictable and foreseeable. Inorder to facilitate such predictability it may be of interest tominimize the volume deviation between the imaginary and practicalsurfaces.

Although the scraping device can expand into the cavity both in thescraping direction and in directions perpendicular thereto, if it in thepreferred way has a sufficient length in the scraping direction forcoverage of the entire cavity, it is believed that the deviation isreduced if it is elongated as described, i.e. with a shorter axis aswell as a longer axis.

In at least on one sense scraping is asymmetrical, namely when thescraping edge enters over the cavity opening, where deflection starts,and even more when the edge leaves the cavity opening, where fulldeflection must decrease, the latter being deemed more important thanthe former. In order to minimize influence of at least the latter effectit is preferred to reduce cavity opening size lateral to the scrapingdirection in relation to the opening size parallel to the scrapingdirection, consistent with an elongated form as discussed. It is furtherpreferred to avoid linear contact between the scraper edge and at leastthe cavity edge when entering or at least when leaving the cavityopening, meaning that point contact is preferred during at leastleaving. This can be achieved by making the scraping edge non-congruentwith the cavity opening leaving edge, e.g. by having a linear scrapingedge and a bent cavity opening leaving edge or vice versa, in the lattercase preferably by a concave scraping edge in order to lift theperipheral scraping edges prior to lifting its central parts whenpassing the cavity opening leaving edge. Alternatively the scraper edgecan meet an elongated cavity opening at an angle with respect to cavityopening longer axis.

In summary, in order to strike a balance between the cavity shape designdictated by filling and the design dictated by scraping, it is preferredthat the cavity has an elongated opening surface and that the fillingdirection and the scraping direction have at least a vector component incommon, preferably a longer vector component in common and mostpreferably are substantially parallel. It is further preferred that atleast the up-flow, and scraping entrance, cavity end wall has a slowslope whereas other cavity wall are steeper.

As indicated, all these observations applies more to larger cavitiesthan to smaller cavities.

BRIEF DESCRIPTION OF THE INVENTION

A non-limiting example of the present inventions will be describedhereinafter with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic partial perspective view showing the apparatusaccording to a first embodiment of the invention in which hidden partsand two cavities are shown in phantom lines.

FIG. 2 is a partial view from above of the apparatus according to afirst embodiment shown in FIG. 1 in which hidden parts and two cavitiesare shown in phantom lines, together with a liquid sample to be tested.

FIG. 3 is a partial sectional side view of the apparatus according to afirst embodiment take along the line A-A in FIG. 2.

FIG. 4 is a partial sectional side view of the apparatus according to afirst embodiment taken along the line A-A in FIG. 2 with the two bodiesA, B moved relatively to each other.

FIG. 5 is a partial view from above of the apparatus according to asecond embodiment provided with an syringe inlet through bore and inwhich hidden parts and two cavities are shown in phantom lines, togetherwith a liquid sample to be tested.

FIG. 6 is a partial sectional side view of the apparatus according to asecond embodiment taken along the line A-A in FIG. 5 provided with asyringe.

FIGS. 5A and 6A depict a slight modification of the embodiment of FIGS.5 and 6 in respect of bore 16′ form and position.

FIG. 7 shows the bore as an insert, in perspective view and in FIGS. 7Aand 7B in sections transverse and along the long slit axis respectively.

FIG. 8 shows a modified embodiment of larger cavity 11′ in anillustrative side view, and in FIGS. 8 a and 8B in sections along thelong and short axes respectively.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1 the apparatus according to a first embodiment comprises twobodies, i.e. a first body comprising a sledge A and a second bodycomprising a framework B, movable relatively to each other and in closecontact. The apparatus forms a part of a disposable support (not shown),preferably in the form of a cassette, and the framework B is formedintegrally with said support. The support comprises at least twochambers, one of which is filled with an accurately defined volume ofdiluent or lysing agent for dilution of a liquid sample, preferably ablood sample, and the other is used for achieving the dilution andmixing of the liquid sample.

The sledge A or the framework B or both are provided with suitableinterengaging means (not shown) so that they can move relative to eachother in close contact.

As can be seen from FIG. 3, between the sledge A and the framework B isa defined channel 3 arranged and provided with at least one inletopening C for a liquid sample 2 (FIG. 2). To facilitate the filling ofthe channel the inlet opening C has in a preferred embodiment aprotrusion 1.

The channel 3 has fluid connection with and extends as an elongation ofsaid at least one inlet opening and beyond at least one accuratelydefined cavity 5. The accurately defined cavity 5 is made in the sledgeA and aligned with said channel 3.

One aspect of the invention is to fill said at least one cavity 5 withthe blood sample in an accurate and repeatable way. The inventors havefound this is best done by capillary force. While not wishing to bebounded by a particular theory, the inventors believe that, by usingcapillary force, the liquid sample forms a wave front in the channelwhich fills said defined channel 3 and said at least one cavity 5 insuch a way that no air bubbles are entrapped in the cavity 5.

By using capillary force for filling, a further aspect of the inventionis achieved in that the accurate filling of said at least one cavity 5is made independent of the direction for filling the apparatus of thedisposable support, whereby the disposable support can be handled in amuch easier way by, for instance, a nurse.

For enabling capillary force to be developed, the defined channel,formed in either the sledge A or the framework B or between the sledgeand the framework, has a particularly chosen form, and the distancebetween the framework and the sledge, i.e. the height of the channel, isbetween 0.05-1.0 mm, preferably 0.1-0.3 mm, and most preferably 0.2 mm.

Below is given an example of how the defined channel can be designed,but the invention should not be regarded as limited to said design.Instead, the inventive conception is that the defined channel is filledwith the liquid sample by capillary force.

In the embodiment shown in the FIGS. 1 and 2 two accurately definedcavities 5, 11 are formed in the sledge. As an example the larger cavity11 has a volume of about 5 μl and the smaller cavity 5 about 0.1 μl, andthe volume of the channel 3 is about 20-40 μl. However, to simplify thedescription of the invention said cavities are described as at least onecavity 5,11.

Thus, according to one aspect of the invention the defined channel 3 hasthe shape of a rectangle in cross section and is formed between thesledge A and the framework B, and one of the long sides of the channel 3is delimited by a rim 4 formed on the sledge A and the other long sideby a recess 6 formed in the framework B. One of the short sides of thechannel 3 forms the inlet opening C and the other short side is open tothe ambient air.

The rim 4 has close contact with the framework B, and on the long sideof the rim opposite to the channel 3 (to the left as seen in FIG. 3) arecess 7 is arranged which stops the liquid sample from furtherspreading due to the fact that the distance between the sledge and theframework is too large for a capillary force to be developed. In asimilar way, the recess 6 also stops the liquid sample from furtherspreading. Thus, only the channel will be filled with the liquid sampleand this is shown in FIG. 2 with dashed lines. However, the physicalmeans that delimit the channel 3 and recess 6 to the right side, as seenin FIG. 3, is a sealing and scraper means 8.

In principle, the design of the defined channel 3 can be made in manyways but according to the invention, it is important that the capillaryforce is stopped by some type of barrier means so that only the definedchannel is filled with the liquid sample.

The sledge A is preferably made of a transparent material so that it iseasily seen when the channel and thereby said at least one cavity 5,11is accurately filled with the liquid sample, and in the case of a bloodsample the defined channel will be seen red.

To further increase the control that said at least one cavity 5,11 isaccurately filled with the liquid sample the sledge A may be providedwith a magnifying means 14, for instance a magnifying glass, which ismade in front of said at least one cavity 5,11, as seen in FIG. 3.

As seen in FIG. 3, for instance, the framework B is provided also withthe sealing and scraper means 8 made of nitrile rubber. The sealing andscraper means 8 has at least one aperture 9 or 9′ aligned with channels15 or 15′ provided in the framework B and in fluid communication withthe at least two chambers in the support (not shown).

In case of blood testing, the channel 3 is filled with blood bycapillary force and when the accurately defined volume of blood is to beachieved and diluted by the accurately defined volume of diluent orlysing agent, the sledge A is moved relative to the framework B, as seenin FIG. 4, so that the sealing and scraper means 8 scrapes off theexcess of blood in the channel 3, whereby an accurately defined volumeof blood is attained in said at least one cavity 5,11. When the sledge Aand the framework are moved relative to each other the rim 4 acts as apusher means for the blood in the channel 3 so that, under nocircumstances, the volume of the blood sample in cavities 5,11 will bechanged. Said at least one cavity 5,11 is brought also in fluidcommunication with the channels 15, 15 ′, respectively through theaperture 9, 9′, respectively, in the sealing and scraper means 8 andthus the diluent or lysing agent containing chambers. The accuratelydefined volume of blood is then mixed with the accurately defined volumeof diluent or lysing agent and thereafter the blood cells are counted.

In a first embodiment according to the invention said at least onecavity 11 has the shape of an elliptical cavity, as seen from above inFIG. 2, and the major axis of the elliptical cavity preferably makes anangle V with the longitudinal direction of the channel 3 of about20-60°. The object of arranging the cavity 11 with said angle is tominimize the risk that, when the sledge A and thereby the cavity 11 ismoved relative the framework B, the leading edge of the sealing andscraper means 8, which moves over the cavity, expand into the cavity dueto the fact that said means is made of a resilient material. If thishappens the accurately defined volume of the liquid sample in the cavitywill change in an unfavourable way. The cavity 11 having a relativelylarge volume (about 5 μl) and the cavity 5 having a relatively smallervolume (about 0.1 μl) are filled by the wave front of the liquid samplefilling the channel 3 without any air bubbles being formed in saidcavities. The smaller cavity 5 can have the form of a half-sphere.

The filling of channel 3 with the liquid sample can be improved if thesurfaces enclosing said channel are made of or coated with a materialselected from the group consisting of dextran, proteins or derivativesthereof or other means or materials known by the artisan that give acontact angle of 75°-0°, preferably 50°-0°, between the blood and thematerial forming the surfaces. It may be enough that only the surface ofsaid at least one cavity 5,11 is coated with the above-mentionedmaterial.

In FIGS. 5 and 6 a second embodiment of the apparatus according to theinvention is shown. The first and the second embodiments of theapparatus according to the invention are made and work in exactly thesame way with the exception of that, in the second embodiment, one ofthe sledge A or the framework B, preferably the framework B, is providedwith a syringe inlet through bore 16 which opens in the channel 3,preferably close to rim 4 (see FIG. 6), and in which a syringe 17,preferably a capillary dispenser commercially available from DrummondScientific Co., the United States, is adapted to be inserted. Thechannel 3 is thus filled with the liquid sample by a combination ofcapillary force and injection when said sample is injected and therebythe cavity 5,11 is filled. Thus, the at least one cavity 5,11 is filledin an accurate and repeatable way as in the first embodiment.

Preferably, the volume of the syringe is adapted to the volume of thechannel 3 so that the channel 3 is not filled too much when the liquidsample is injected, whereby losses of liquid sample can be avoided.

An advantage when using a syringe for filling the channel 3 is that theliquid sample to be tested can be drawn from a test tube or from anyother means, especially in veterinary applications.

FIGS. 5A and 6A depict a slight modification of the embodiment shown inFIGS. 5 and 6 in respect of bore 16′ form and position. The bore is herelocated in between the cavities 5,11, minimizing the flow distance forthe liquid to reach the cavities. Furthermore, the bore is here given anelongated slit shape and positioned with the slit longer sides exposedtowards the cavities, i.e. in the direction of the desired liquid flow.

FIG. 7 shows the bore 16′ as an insert, in perspective view and in FIGS.7A and 7B in sections transverse and along the long slit axisrespectively. Sample is intended to be provided from above, i.e. liquidflow is from above to below in the Figures. Sample can be providedeither by a liquid drop placed directly on the slit or by an ejectioninstrument, e.g. the syringe 17, inserted into the bore upper part, andpreferably then with a broad enough instrument tip to be stopped by thehour-glass narrowest section. As clearly seen in the cross-sections thebore 16′ has the overall shape of an hour-glass with upper sidesconverging with a larger angle than the angle of the diverging lowersides. If the diverging angle is too large, or not diverging at all,liquid flow may not transfer properly into the channel below.

Moreover, in the embodiment shown in FIGS. 7, 7A, and 7B, respectively,the bore 16′ has the shape of a elongated slit shaped funnel ending inthe capillary channel, preferably having stopping devices against toodeep penetration of the ejection instrument. In case of non-capillaryfeeding the bore 16′ preferably has a narrowest flow area preferablybeing larger than that required for capillary feeding, thereby assistingin gravity filling, preferably, however, being noncircular, preferablyslit-formed, for proper transition between non-capillary and capillaryflow. For similar reasons the funnel preferably has a diverging portionafter its narrowest part, giving an overall shape of an hour-glass, witha diverging outlet angle adapted for capillary flow.

FIGS. 8, 8A, and 8 b show a modified preferred embodiment of said atleast one cavity 11′ in which said at least one larger cavity 11′ isdesigned for facilitated capillary filling. Said at least one largercavity 11′ is preferably shaped elongated, i.e. having an imaginarysurface with a longer axis and a shorter axis perpendicular thereto,which gives an increased circumference to area ratio in relation to acircle, which elongated shape can take a variety of forms such aselliptical, rectangular etc. Preferably the cavity 11′ has a generalwedge like shape.

With reference to FIG. 8A, illustrating section A-A of FIG. 8, theliquid is intended to be fed from right and flow towards left in saidFigure. As clearly seen in this section, at the right, up-flow, end theliquid flows into the cavity 11′ along a more level slope, with asmaller angle α, than at the left, down-flow, end where the liquid flowsout from the cavity 11′ along a more steep slope, having a larger angleβ.

As seen in FIG. 8B, illustrating section B-B of FIG. 8, the sides of thecavity 11′ parallel with the intended liquid flow are steep,substantially with a 90° angle relative to the reference surface orchannel 3.

The elongated form secures that the cavity 11′ has an increase surfaceto volume ratio in relation to the minimal possible. Furthermore, thesides of cavity 11′ substantially parallel to the flow direction aresteep with respect to the reference surface.

It should be noted that the apparatus according to the second embodimentand the modified embodiments shown above also can be filled in the sameway as the apparatus according to the first embodiment, i.e. theprotrusion 1 is dipped down in the liquid sample 2, whereby the channel3 and the cavities 5,11 and 11′ are filled with the sample by capillaryforce. Thus, the syringe inlet through bore 16, 16′ does not affect thecapillary force in the channel.

1. An apparatus for filling a sample volume defining device forseparating at least one defined volume of a liquid sample from arelatively larger undefined volume of said sample, said devicecomprising: a) A first body and a second body movable relative to saidfirst body, whereby said first body has at least one cavity in a surfacethereof, said at least one cavity having a defined volume, and saidsecond body includes a sealing and scraper means slidable along saidsurface and over said at least one cavity upon relative movement of saidbodies whereby said accurately defined volume is achieved in said atleast one cavity; b) A channel formed between said first and secondbodies, disposed above and enclosing an area around said cavity on saidupper surface of said first body, said channel having dimensions inwidth and length that facilitate capillary filling; and c) An inletopening and a further opening to ambient air, both in fluidcommunication with said channel between said first and second bodies,said inlet opening adapted to fill a liquid sample therethrough intosaid channel, said cavity located between said inlet opening and saidfurther opening to ambient air, said inlet opening positioned beyondsaid cavity at an up-flow direction with a distance along said uppersurface of said first body from said cavity, and at the same time beingin communication with said cavity through an enclosed space within saidchannel, said further opening to ambient air positioned at a down-flowdirection of said cavity Wherein when said liquid sample is filledthrough said inlet opening into said channel, said liquid sample flowsacross said distance on said upper surface of said first body withinsaid channel, with a wave front from said up-flow direction to saiddown-flow direction across said cavity, thereby said liquid sample fillssaid cavity in a manner than no air bubbles are entrapped in saidcavity.
 2. The device of claim 1, wherein said sealing and scraper meansis made of a resilient material.
 3. The device of claim 2, wherein saidsealing and scraper means includes at least one aperture aligned withand in fluid communication with a pair of through-channels of saidsecond body; and when said first body is slid, said cavity containingsaid defined volume of said liquid sample is then positioned incommunication with said pair of through-channels of said second bodythrough said aperture of said sealing and scraper means.
 4. The deviceof claim 1, wherein said inlet opening is disposed through said secondbody, beyond said cavity on said upper surface of said first body,adapted to fill said liquid sample therethrough by injection.
 5. Thedevice of claim 1, wherein said channel between said first and secondbodies is filled by gravity filling.
 6. The device of claim 1, wherein aheight of the channel is about 0.05-1.0 mm.
 7. The device of claim 1,wherein said channel has a volume of about 20 to 40 microliter (μl). 8.The device of claim 1, wherein said cavity has a volume of less than 15μl.
 9. The device of claim 1, wherein said cavity has a volume of about5 μl.
 10. The device of claim 1, wherein a surface of said channel iscoated with a material selected from the group consisting of dextran,proteins or derivatives thereof.
 11. The device of claim 1, wherein atleast a surface of said cavity is coated with a material selected fromthe group consisting of dextran, proteins or derivatives thereof. 12.The device of claim 11, wherein said surface of said cavity is coatedwith a material that gives a contact angle of 75°-0° between said liquidsample and a material forming the surface of said cavity.
 13. The deviceof claim 1, wherein said cavity is elongated with a long axis and ashort axis perpendicular thereto, and has a cross section along saidlong axis of a wedge like shape with a first end wall having a slowdescending slope down to a bottom of said cavity; said cavity beingorientated with said long axis in said up-flow direction, with saidfirst end wall as an up-flow end and a second end wall as a down flowend of said cavity.
 14. The device of claim 13, wherein said first andsecond end walls have different slopes and said second end wall has asteeper slope than said that of said first end wall.
 15. The device ofclaim 14, wherein two sides of said cavity parallel to said long axis ofsaid cavity have a steep slope.
 16. The device of claim 1, wherein saidfirst body is provided with a magnifying means in front of said cavityon a side opposing said upper surface.
 17. The device of claim 1,wherein said first body further comprises a second cavity on said uppersurface thereof, having a second defined volume different from that ofsaid at least one cavity, said channel between said first and secondbodies being above and enclosing an area around said second cavity andsaid inlet opening being beyond both of said cavities; wherein when saidliquid sample is filled through said inlet opening into said channel,said liquid sample flows on said upper surface of said first body withinsaid channel across said second cavity, with a wave front from anup-flow direction to a down-flow direction in reference to said secondcavity, thereby said liquid sample fills said second cavity in a mannerthat no air bubbles are entrapped in said second cavity.
 18. The deviceof claim 17, wherein when said first body is slid against said secondbody said sealing and scraper means scrapes said liquid sample above andaround both of said cavities, obtaining two different defined volumes ofsaid liquid sample in said cavities, respectively.
 19. The device ofclaim 18, wherein said sealing and scraper means includes two apertures,each thereof aligned with and in fluid communication with one of twopairs of through-channels of said second body; and when said first bodyis slid, each of said cavities containing respective defined volume ofsaid liquid sample is positioned in communication with said two pairs ofthrough-channels of said second body through said apertures of saidsealing and scraper means, respectively.